Conductive coordination polymers(CCPs)have shown great potential for electronic purposes.However,their applications in photodetection have been limited by poor sensitivity,low on/off current ratio,and slow response ow...Conductive coordination polymers(CCPs)have shown great potential for electronic purposes.However,their applications in photodetection have been limited by poor sensitivity,low on/off current ratio,and slow response owing to the low charge generation and/or separation efficiency.In this work,metal-to-ligand chargetransfer(MLCT)in PhSeAg was used to fabricate a single-component MLCT photodetecting material for the first time to solve the above challenges.The material obtained possesses ultrahigh sensitivity to weak-light intensity(0.03 mW cm^(−2)),the highest on/off ratio,and the fastest response speed than other wellknown CCPs materials tested.Our work might provide a simple but common strategy for designing high-performance CCPs composites for optoelectrical applications.展开更多
针对现有直流断路器存在的分断故障电流峰值高、通态损耗大、成本高以及机械开关电弧等问题,提出一种基于电容换流的限流型高压直流断路器(current-limiting high-voltage DC circuit breaker based on capacitor commutation,CC&CL...针对现有直流断路器存在的分断故障电流峰值高、通态损耗大、成本高以及机械开关电弧等问题,提出一种基于电容换流的限流型高压直流断路器(current-limiting high-voltage DC circuit breaker based on capacitor commutation,CC&CL-HDCCB)拓扑。正常运行时系统电流仅流过机械开关,导通损耗小;当进行故障开断操作时,投入电容进行充电,利用较高的电容电压提供电力电子器件的导通电压,使故障电流从机械开关支路转移,可用于高电压等级工况;换流支路与限流支路共同作用避免了故障电流的自然上升过程,有效降低了故障电流峰值。对断路器故障处理过程中的机械开关耐压和各支路电流等方面进行分析,给出了合理的元件参数和运行方式。最后利用PSCAD/EMTDC软件进行仿真验证,与相关断路器就故障电流峰值、避雷器吸能、电容电压等方面进行对比分析,验证了所提结构的合理性和经济性。展开更多
Mass customization (MC) is emerging as a competitive advantage of firms with the intensified competition and economic globalization.As a key feature of MC,postponement strategy postpones activities in the supply chain...Mass customization (MC) is emerging as a competitive advantage of firms with the intensified competition and economic globalization.As a key feature of MC,postponement strategy postpones activities in the supply chain until customer orders are received.This article provides a review of the literature on postponement from perspectives of research content and methodology.Taking postponement as a supply chain concept,this article specifically reclassifies the postponement applications according to the positioning of the customer order decoupling point (CODP) in the supply chain.Future directions for postponement research are also suggested in this article.展开更多
The community structures of phytoplankton are important factors and indicators of lake water quality. Harmful algal blooms severely impact water supply, recreational activities and wildlife habitat. This study aimed t...The community structures of phytoplankton are important factors and indicators of lake water quality. Harmful algal blooms severely impact water supply, recreational activities and wildlife habitat. This study aimed to examine the phytoplankton composition and variations using microscopy, and identify harmful Cyanobacteria in weekly samples taken from four sites at Harsha Lake in southwest Ohio. Over the course of the summer in 2015, the phytoplankton of Harsha Lake consisted mainly of 13 taxa belonging to Bacillariophyta, Chlorophyta, Cryptophyta, Cyanobacteria, Dinophyta and Euglenophyta. Their significant successions started with Bacillariophyta and/or Chlorophyta, then bloomed with Cyanobacteria and ended with Chlorophyta and/or Dinophyta. Cyanobacteria members: Microcystis, Planktothrix, Dolichospermum, Aphanizomenon, Cylindrospermopsis, and Oscillatoria from the Cyanophyceae were identified to be dominant genera. These organisms varied spatially and temporally in similar patterns along with the variations of nutrients and formed the summer bloom with the total biomasses ranging from 0.01 to 114.89 mg L-1 with mean of 22.88 mg L-1. M. aeruginosa and P. rubescens were revealed as the microcystin producers, while A. circinalis and Aphanizomenon sp. were identified as a saxitoxin producer through cloning and sequencing PCR products of mcyA, mcyE and sxtA genes. The biomasses of phytoplankton, Cyanobacteria and Microcystis were positively correlated to nutrients, especially to total nitrogen. The total ELISA measurement for microcystin positively correlated with Cyanobacteria (R2 = 0.66, P Microcystis (R2 = 0.64, P 2 = 0.59, P < 0.0001). The basic information on the occurrence and biomasses of Cyanobacteria and total phytoplankton, and the analysis for toxic species, which were the first report for the inland water in Ohio, USA, will document the succession patterns of phytoplankton and toxin production over a season and provide data to predict risk occurrence to both human and ecological factors.展开更多
Objective To investigate genetic and antibiotic resistance characteristics of Campylobacter jejuni(C. jejuni) isolated from Shenzhen. Methods Multilocs sequence typing and agar dilution methods were used to define the...Objective To investigate genetic and antibiotic resistance characteristics of Campylobacter jejuni(C. jejuni) isolated from Shenzhen. Methods Multilocs sequence typing and agar dilution methods were used to define the genotype and antibiotic resistance of C. jejuni, respectively. Results In total, 126 C. jejuni strains were isolated. The prevalence of C. jejuni was 5.3% in diarrheal patients. The prevalence in poultry meat(36.5%) was higher than that in cattle meat(1.1%). However, the prevalence in poultry cloacal swabs(27.0%) was lower than that in cattle stool(57.3%). Sixty-two sequence types were obtained, among which 27 of the STs and 10 alleles were previously unreported. The most frequently observed clonal complexes were ST-21(11.9%), ST-22(10.3%), and ST-403(7.1%). ST-21, ST-45, ST-354, ST-403, and ST-443 complexes overlapped between isolates from patients and cattle, whereas ST-45 and ST-574 complexes overlapped between isolates from patients and poultry. All C. jejuni were resistant to at least one antibiotic. The highest resistance rate was toward ciprofloxacin(89.7%), followed by tetracycline(74.6%), and nalidixic acid(69.0%). Conclusion This is the first report of the genotypes and antibiotic resistance of C. jejuni in Shenzhen. Overlapping clonal complexes were found between isolates from patients and cattle, and between patients and poultry.展开更多
Manure and fertilizer applications can increase soil productivity and land economic values, but the controversial result can be a decline of water quality due to the increased nutrient exports from soils to the stream...Manure and fertilizer applications can increase soil productivity and land economic values, but the controversial result can be a decline of water quality due to the increased nutrient exports from soils to the streams. The impacts of landuse, manure and fertilizer application on nutrient exports from soils to the streams were analyzed using the SWAT (Soil Water Assessment Tool) model for the Salmon River watershed in south-central British Columbia, Canada. The results showed that the animal farms had the highest rates of nutrient exports from soils to the streams and the natural forested lands had the lowest. It was estimated that the whole Salmon River watershed would export approximately 11.52 t·yr-1 of organic nitrogen (ON), 8.05 t·yr-1 of nitrate nitrogen (NO3-N), 2.30 t·yr-1 of organic phosphorus (OP) and 1.36 t·yr-1 of soluble reactive phosphorus (SRP) if the whole watershed was covered by natural vegetation without human disturbance. Current landuse changes, by converting natural vegetation lands to agriculture and animal farms and associated manure and fertilizer applications, have in-creased approximately 53.30 t·yr-1 of ON, 9.68 t·yr-1 of NO3-N, 22.69 t·y-1 of OP and 6.23 t·y-1 of SRP exports to the streams in the whole watershed. The SWAT model predicted that a daily 100 kg·ha-1 of fresh manure deposit from grazing cows during grazing season from later spring to later fall could increase 2.57 kg·ha-1·yr-1 of ON, 0.39 kg·ha-1·yr-1 of NO3-N, 2.35 kg·ha-1·yr-1 of OP and 0.48 kg·ha-1·yr-1 of SRP export to the streams. Fertilization could increase 1.57 kg ha-1 yr-1 of ON and 4.02 kg·ha-1·yr-1 of NO3-N export to the streams if 100 kg·ha-1·yr-1 of nitrogen (NH4NO3) fertilizer was applied in spring. Also fertilization could increase 1.18 kg·ha-1·yr-1 of OP and 0.20 kg·ha-1·yr-1 of SRP export to the streams if 100 kg·ha-1 phosphorus (P2O5) fertilizer was applied in spring.展开更多
Lake Michigan, the sixth largest freshwater lake in the world by surface area, was utilized as a water body for assessment. Field data collected at sampling sites throughout the lake in an intensive monitoring effort ...Lake Michigan, the sixth largest freshwater lake in the world by surface area, was utilized as a water body for assessment. Field data collected at sampling sites throughout the lake in an intensive monitoring effort were utilized for evaluation of the distribution of sediment measurements. An assessment of sediment nutrient and carbon measurements within Lake Michigan was completed to recognize strata resulting from the hydrodynamics of the system. Nonparametric comparison tests revealed that significant differences exist between measurements of sediment nutrients and organic carbon in the lake using strata based upon water column depth (all results demon-strated a p < 0.05, α = 0.05). Cross-validation analysis was applied to the field-collected samples, revealing that large errors occur when estimating sediment flux of carbon or nutrients at a given location in the lake without considering stratification of the distributions of these measurements. Errors in estimating sediment concentrations of nutrients and carbon specific to a location in the lake demonstrated a statistically significant increase when stratification of sediment measurements wasn’t employed among sites. For example, distributions of errors in estimating all nutrients and organic carbon concentrations, whereby distance squared inverse interpolation methods were applied, demonstrated a statistically significant increase in absence of stratification (all p < 0.001, α = 0.05). These results have implications for characterization, monitoring, and modeling sediment and water interaction as related to eutrophication, as well as to contaminant exposure and bioaccumulation for chemicals within Lake Michigan and large water bodies where stratification of the sediment based upon physics of the system exists.展开更多
A controlled laboratory study was conducted to measure the dispersion effectiveness of Corexit 9500 on 23 different crude oils. This study was a part of a larger project initiated by the Bureau of Safety and Environme...A controlled laboratory study was conducted to measure the dispersion effectiveness of Corexit 9500 on 23 different crude oils. This study was a part of a larger project initiated by the Bureau of Safety and Environmental Enforcement (BSEE) testing 20 oils to compare the predictive value of laboratory dispersant effectiveness tests with their larger scale test conducted at Ohmsett, BSEE’s national oil spill response test facility located in Leonardo, NJ. The test used in this study was the Baffled Flask Test (BFT), which is planned for adoption as EPA’s official testing protocol for listing commercial dispersant products on the National Contingency Plan Product Schedule, replacing the current Swirling Flask Test (SFT) [1]. In addition, the results of 3 additional oils, the 2 used in the SFT and BFT as currently written plus another reference oil, are presented. The temperature used for the tests was 15°C, to match the temperature used at Ohmsett. The dispersion effectiveness ranged from 3.4% to 93%. The BFT is a laboratory test with results that are inversely correlated with oil viscosity and therefore has predictive value in the decision to use a dispersant in the event of a spill.展开更多
INTRODUCTION Poly-and perfluorinated alkyl substances(PFASs)are manufactured chemicals made of fluorine atoms bonded to a carbon chain with a terminal functional group.PFASs are highly resistant to oil,water,chemicals...INTRODUCTION Poly-and perfluorinated alkyl substances(PFASs)are manufactured chemicals made of fluorine atoms bonded to a carbon chain with a terminal functional group.PFASs are highly resistant to oil,water,chemicals,and heat,due to strong C−F bonds;therefore,they have been extensively used in various industrial applications,including but not limited to automotive,wrapping,cookware,and clothing.^(1)However,an increasing number of studies have identified adverse impacts of PFAS exposure on human health.^(2)Despite the growing concern of human exposure to PFAS by drinking water,PFAS removal from water remains a challenging issue as conventional water treatment methods(e.g.,flocculation,sedimentation,or biodegradation)are not capable of treating a broad array of PFAS compounds.展开更多
基金This work was supported by the NSF of China(21822109,21805276,21773245,21773151,21975254)National Key R&D Program of China(2017YFA0206802)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB20000000)Key Research Program of Frontier Science,Chinese Academy of Sciences(QYZDB-SSW-SLH023)Youth Innovation Promotion Association CAS,International Partnership Program of CAS(121835KYSB201800).
文摘Conductive coordination polymers(CCPs)have shown great potential for electronic purposes.However,their applications in photodetection have been limited by poor sensitivity,low on/off current ratio,and slow response owing to the low charge generation and/or separation efficiency.In this work,metal-to-ligand chargetransfer(MLCT)in PhSeAg was used to fabricate a single-component MLCT photodetecting material for the first time to solve the above challenges.The material obtained possesses ultrahigh sensitivity to weak-light intensity(0.03 mW cm^(−2)),the highest on/off ratio,and the fastest response speed than other wellknown CCPs materials tested.Our work might provide a simple but common strategy for designing high-performance CCPs composites for optoelectrical applications.
文摘针对现有直流断路器存在的分断故障电流峰值高、通态损耗大、成本高以及机械开关电弧等问题,提出一种基于电容换流的限流型高压直流断路器(current-limiting high-voltage DC circuit breaker based on capacitor commutation,CC&CL-HDCCB)拓扑。正常运行时系统电流仅流过机械开关,导通损耗小;当进行故障开断操作时,投入电容进行充电,利用较高的电容电压提供电力电子器件的导通电压,使故障电流从机械开关支路转移,可用于高电压等级工况;换流支路与限流支路共同作用避免了故障电流的自然上升过程,有效降低了故障电流峰值。对断路器故障处理过程中的机械开关耐压和各支路电流等方面进行分析,给出了合理的元件参数和运行方式。最后利用PSCAD/EMTDC软件进行仿真验证,与相关断路器就故障电流峰值、避雷器吸能、电容电压等方面进行对比分析,验证了所提结构的合理性和经济性。
基金National Natural Science Foundation of ChinaMinistry of Science&Technology of China and Scientific and Technological Innovation Foundation for Graduate Students of Huazhong University of Science and Technology for the financial support through grant 79970026,a National 863/CIMS Scheme grant 2001AA414110 and grant YCJ-02-005 respectively.
文摘Mass customization (MC) is emerging as a competitive advantage of firms with the intensified competition and economic globalization.As a key feature of MC,postponement strategy postpones activities in the supply chain until customer orders are received.This article provides a review of the literature on postponement from perspectives of research content and methodology.Taking postponement as a supply chain concept,this article specifically reclassifies the postponement applications according to the positioning of the customer order decoupling point (CODP) in the supply chain.Future directions for postponement research are also suggested in this article.
文摘The community structures of phytoplankton are important factors and indicators of lake water quality. Harmful algal blooms severely impact water supply, recreational activities and wildlife habitat. This study aimed to examine the phytoplankton composition and variations using microscopy, and identify harmful Cyanobacteria in weekly samples taken from four sites at Harsha Lake in southwest Ohio. Over the course of the summer in 2015, the phytoplankton of Harsha Lake consisted mainly of 13 taxa belonging to Bacillariophyta, Chlorophyta, Cryptophyta, Cyanobacteria, Dinophyta and Euglenophyta. Their significant successions started with Bacillariophyta and/or Chlorophyta, then bloomed with Cyanobacteria and ended with Chlorophyta and/or Dinophyta. Cyanobacteria members: Microcystis, Planktothrix, Dolichospermum, Aphanizomenon, Cylindrospermopsis, and Oscillatoria from the Cyanophyceae were identified to be dominant genera. These organisms varied spatially and temporally in similar patterns along with the variations of nutrients and formed the summer bloom with the total biomasses ranging from 0.01 to 114.89 mg L-1 with mean of 22.88 mg L-1. M. aeruginosa and P. rubescens were revealed as the microcystin producers, while A. circinalis and Aphanizomenon sp. were identified as a saxitoxin producer through cloning and sequencing PCR products of mcyA, mcyE and sxtA genes. The biomasses of phytoplankton, Cyanobacteria and Microcystis were positively correlated to nutrients, especially to total nitrogen. The total ELISA measurement for microcystin positively correlated with Cyanobacteria (R2 = 0.66, P Microcystis (R2 = 0.64, P 2 = 0.59, P < 0.0001). The basic information on the occurrence and biomasses of Cyanobacteria and total phytoplankton, and the analysis for toxic species, which were the first report for the inland water in Ohio, USA, will document the succession patterns of phytoplankton and toxin production over a season and provide data to predict risk occurrence to both human and ecological factors.
基金supported by Sanming Project of Medicine in Shenzhen[SZSM201803081]Shenzhen Technology and Innovation Plan,China[JCYJ 20140416095154399]Nanshan District Technology and Innovation Plan,Shenzhen,China[2016064]
文摘Objective To investigate genetic and antibiotic resistance characteristics of Campylobacter jejuni(C. jejuni) isolated from Shenzhen. Methods Multilocs sequence typing and agar dilution methods were used to define the genotype and antibiotic resistance of C. jejuni, respectively. Results In total, 126 C. jejuni strains were isolated. The prevalence of C. jejuni was 5.3% in diarrheal patients. The prevalence in poultry meat(36.5%) was higher than that in cattle meat(1.1%). However, the prevalence in poultry cloacal swabs(27.0%) was lower than that in cattle stool(57.3%). Sixty-two sequence types were obtained, among which 27 of the STs and 10 alleles were previously unreported. The most frequently observed clonal complexes were ST-21(11.9%), ST-22(10.3%), and ST-403(7.1%). ST-21, ST-45, ST-354, ST-403, and ST-443 complexes overlapped between isolates from patients and cattle, whereas ST-45 and ST-574 complexes overlapped between isolates from patients and poultry. All C. jejuni were resistant to at least one antibiotic. The highest resistance rate was toward ciprofloxacin(89.7%), followed by tetracycline(74.6%), and nalidixic acid(69.0%). Conclusion This is the first report of the genotypes and antibiotic resistance of C. jejuni in Shenzhen. Overlapping clonal complexes were found between isolates from patients and cattle, and between patients and poultry.
文摘Manure and fertilizer applications can increase soil productivity and land economic values, but the controversial result can be a decline of water quality due to the increased nutrient exports from soils to the streams. The impacts of landuse, manure and fertilizer application on nutrient exports from soils to the streams were analyzed using the SWAT (Soil Water Assessment Tool) model for the Salmon River watershed in south-central British Columbia, Canada. The results showed that the animal farms had the highest rates of nutrient exports from soils to the streams and the natural forested lands had the lowest. It was estimated that the whole Salmon River watershed would export approximately 11.52 t·yr-1 of organic nitrogen (ON), 8.05 t·yr-1 of nitrate nitrogen (NO3-N), 2.30 t·yr-1 of organic phosphorus (OP) and 1.36 t·yr-1 of soluble reactive phosphorus (SRP) if the whole watershed was covered by natural vegetation without human disturbance. Current landuse changes, by converting natural vegetation lands to agriculture and animal farms and associated manure and fertilizer applications, have in-creased approximately 53.30 t·yr-1 of ON, 9.68 t·yr-1 of NO3-N, 22.69 t·y-1 of OP and 6.23 t·y-1 of SRP exports to the streams in the whole watershed. The SWAT model predicted that a daily 100 kg·ha-1 of fresh manure deposit from grazing cows during grazing season from later spring to later fall could increase 2.57 kg·ha-1·yr-1 of ON, 0.39 kg·ha-1·yr-1 of NO3-N, 2.35 kg·ha-1·yr-1 of OP and 0.48 kg·ha-1·yr-1 of SRP export to the streams. Fertilization could increase 1.57 kg ha-1 yr-1 of ON and 4.02 kg·ha-1·yr-1 of NO3-N export to the streams if 100 kg·ha-1·yr-1 of nitrogen (NH4NO3) fertilizer was applied in spring. Also fertilization could increase 1.18 kg·ha-1·yr-1 of OP and 0.20 kg·ha-1·yr-1 of SRP export to the streams if 100 kg·ha-1 phosphorus (P2O5) fertilizer was applied in spring.
文摘Lake Michigan, the sixth largest freshwater lake in the world by surface area, was utilized as a water body for assessment. Field data collected at sampling sites throughout the lake in an intensive monitoring effort were utilized for evaluation of the distribution of sediment measurements. An assessment of sediment nutrient and carbon measurements within Lake Michigan was completed to recognize strata resulting from the hydrodynamics of the system. Nonparametric comparison tests revealed that significant differences exist between measurements of sediment nutrients and organic carbon in the lake using strata based upon water column depth (all results demon-strated a p < 0.05, α = 0.05). Cross-validation analysis was applied to the field-collected samples, revealing that large errors occur when estimating sediment flux of carbon or nutrients at a given location in the lake without considering stratification of the distributions of these measurements. Errors in estimating sediment concentrations of nutrients and carbon specific to a location in the lake demonstrated a statistically significant increase when stratification of sediment measurements wasn’t employed among sites. For example, distributions of errors in estimating all nutrients and organic carbon concentrations, whereby distance squared inverse interpolation methods were applied, demonstrated a statistically significant increase in absence of stratification (all p < 0.001, α = 0.05). These results have implications for characterization, monitoring, and modeling sediment and water interaction as related to eutrophication, as well as to contaminant exposure and bioaccumulation for chemicals within Lake Michigan and large water bodies where stratification of the sediment based upon physics of the system exists.
文摘A controlled laboratory study was conducted to measure the dispersion effectiveness of Corexit 9500 on 23 different crude oils. This study was a part of a larger project initiated by the Bureau of Safety and Environmental Enforcement (BSEE) testing 20 oils to compare the predictive value of laboratory dispersant effectiveness tests with their larger scale test conducted at Ohmsett, BSEE’s national oil spill response test facility located in Leonardo, NJ. The test used in this study was the Baffled Flask Test (BFT), which is planned for adoption as EPA’s official testing protocol for listing commercial dispersant products on the National Contingency Plan Product Schedule, replacing the current Swirling Flask Test (SFT) [1]. In addition, the results of 3 additional oils, the 2 used in the SFT and BFT as currently written plus another reference oil, are presented. The temperature used for the tests was 15°C, to match the temperature used at Ohmsett. The dispersion effectiveness ranged from 3.4% to 93%. The BFT is a laboratory test with results that are inversely correlated with oil viscosity and therefore has predictive value in the decision to use a dispersant in the event of a spill.
文摘INTRODUCTION Poly-and perfluorinated alkyl substances(PFASs)are manufactured chemicals made of fluorine atoms bonded to a carbon chain with a terminal functional group.PFASs are highly resistant to oil,water,chemicals,and heat,due to strong C−F bonds;therefore,they have been extensively used in various industrial applications,including but not limited to automotive,wrapping,cookware,and clothing.^(1)However,an increasing number of studies have identified adverse impacts of PFAS exposure on human health.^(2)Despite the growing concern of human exposure to PFAS by drinking water,PFAS removal from water remains a challenging issue as conventional water treatment methods(e.g.,flocculation,sedimentation,or biodegradation)are not capable of treating a broad array of PFAS compounds.
